JP2005170287A - Hydraulic brake device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent loss of liquid amount balance in a master cylinder after an on-off valve is opened to supply working fluid from the master cylinder to a wheel cylinder, in a hydraulic brake device for communicating the wheel cylinder that receives hydraulic pressure from another pressure source and generates a braking force with the master cylinder for generating the hydraulic pressure according to an operator's input operation via the on-off valve. <P>SOLUTION: A master cylinder passage 14 is provided with a responsiveness improving piston 22 in parallel with the on-off valve 15. The on-off valve 15 is cut off, and the responsiveness improving piston 22 receives the working fluid from the master cylinder 10 and supplies the master cylinder hydraulic pressure to the wheel cylinder 6. After that, when the pump hydraulic pressure of a hydraulic pump 1 becomes high or a braking operation is lost, the responsiveness improving piston 22 returns working fluid of which amount is the same as that of the supplied working fluid to the master cylinder 10. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, the on-off valve in the pipe line from the master cylinder to the wheel cylinder is closed, and the hydraulic pressure from another hydraulic pressure source is adjusted based on the detected value of the master cylinder hydraulic pressure and directed toward the wheel cylinder. The present invention relates to a so-called brake-by-wire hydraulic brake device, and more particularly to a technology for improving responsiveness to alleviate a delay in generation of wheel cylinder hydraulic pressure with respect to a driver's braking operation.

As a brake-by-wire type hydraulic brake device, a device as described in Patent Document 1 has been known.
Japanese Patent Laid-Open No. 9-20229 (FIG. 12)

In the hydraulic brake device described in Patent Document 1, an opening / closing valve is inserted in a conduit for directing hydraulic pressure from a master cylinder that responds to a braking operation to a wheel cylinder, and a conduit between the opening / closing valve and the wheel cylinder is provided. Another hydraulic pressure source (consisting of a pump and an accumulator) is provided in connection with the portion.
During the braking operation, the other hydraulic pressure source is driven with the open / close valve closed, and the hydraulic pressure from the hydraulic pressure source is adjusted based on the detected value of the master cylinder hydraulic pressure and directed to the wheel cylinder. Wheel braking can be performed.

  By the way, in the configuration in which another hydraulic pressure source is operated only at the time of braking operation, the master cylinder fluid is used when the hydraulic pressure increase rate generated by the other hydraulic pressure source is low, such as immediately after the start of the operation of the other hydraulic pressure source. While sufficient pressure is supplied directly to the wheel cylinder, sufficient hydraulic pressure cannot be supplied to the wheel cylinder. In that case, the on-off valve is opened until the hydraulic pressure generated by another hydraulic pressure source rises above the master cylinder hydraulic pressure, and when the master cylinder hydraulic pressure is reached, the on-off valve is shut off and another hydraulic pressure source is used. By supplying the generated hydraulic pressure to the wheel cylinder, it is conceivable to supply a sufficient hydraulic pressure to the wheel cylinder by supplementing a place where the response of another hydraulic pressure source is poor.

However, the conventional hydraulic brake device has the following problems. In other words, since the on / off valve is shut off during the braking operation to switch from the master cylinder hydraulic pressure to the hydraulic pressure of another hydraulic source, the amount of operation supplied from the master cylinder to the wheel cylinder side while the on / off valve is open. The liquid is not returned to the master cylinder, and the balance of the liquid volume in the master cylinder does not match.
For this reason, operability deteriorates, for example, the pedal stroke is shortened after the brake pedal is depressed, or the initial position of the brake pedal is changed.

  Even when supplying hydraulic pressure from the master cylinder to the wheel cylinder side, the present invention prevents the master cylinder's fluid balance from being lost, and the initial position of the brake pedal changes and the maximum stroke The purpose is to solve the problem that the operability is deteriorated due to the shortening.

For this purpose, the hydraulic brake device according to the invention is as claimed in claim 1,
An on-off valve is inserted in the pipe line that directs the hydraulic pressure from the master cylinder that responds to the braking operation to the wheel cylinder, and another hydraulic pressure source is provided by connecting to the pipe line part between the on-off valve and the wheel cylinder, When the braking operation occurs, the other hydraulic pressure source is driven with the on-off valve closed, and the hydraulic pressure from the hydraulic pressure source is adjusted based on the detected value of the master cylinder hydraulic pressure, and the wheel In the hydraulic brake device that is directed to the cylinder,
Response improvement means having a piston that responds to a differential pressure between the master cylinder side hydraulic pressure and the wheel cylinder side hydraulic pressure before and after the on-off valve is provided.

  According to the hydraulic brake device of the present invention, when the hydraulic pressure of another pressure source is lower than the master cylinder hydraulic pressure, such as immediately after the operation of the other pressure source is started, the master cylinder hydraulic pressure is set via the response improving means. When the hydraulic pressure of another pressure source becomes higher than the master cylinder hydraulic pressure or when the braking operation is stopped, the response improving means supplies the hydraulic fluid supplied from the master cylinder side to the master cylinder side. Therefore, even if the master cylinder hydraulic pressure is supplied to the wheel cylinder, the pedal stroke and the initial position of the brake pedal are prevented from changing.

Hereinafter, embodiments of the present invention will be described in detail based on examples shown in the drawings.
FIG. 1 exemplifies a hydraulic circuit of a hydraulic brake device according to the present invention, and shows only one of the wheel cylinders of a braking unit provided on each wheel.
First, the circuit configuration of the present embodiment will be described. A hydraulic pump 1 that receives a driving force from a motor (not shown) and can pump high-pressure hydraulic fluid during braking is connected to a high-pressure source passage 2. The high-pressure source passage 2 is connected to the master cylinder passage 14, and the wheel cylinder side 3 becomes the wheel cylinder passage 3 from the connection location 2 j. The wheel cylinder passage 3 is connected to a wheel cylinder 6 provided in a caliper that brakes the wheel 5. A check valve 7 is inserted at a location where the high pressure source passage 2 is connected to the hydraulic pressure pump 1 to allow the hydraulic fluid to flow from the hydraulic pressure pump 1 to the wheel cylinder side and prevent backflow.

A brake pedal 8 that is depressed by the driver is attached to the master cylinder 10 via a push rod 9. The master cylinder 10 converts the pedaling force of the driver into hydraulic fluid pressure (master cylinder hydraulic pressure).
The master cylinder 10 communicates with the wheel cylinder 6 via the master cylinder passage 14 and the wheel cylinder passage 3. An open / close valve 15 is inserted in the master cylinder passage 14.
A reservoir tank 11 provided in the upper part of the master cylinder 10 communicates with the hydraulic pump 1 through a reservoir passage 12 so that hydraulic fluid can be supplied to the hydraulic pump 1. The reservoir passage 12 is connected to the reservoir passages 12a and 12b at a connection location 12j. The reservoir passage 12a is connected to the high-pressure source passage 2, but a relief valve 13 is provided in the reservoir passage 12a, and the high-pressure source passage 2 is connected to the reservoir passage 12 only when the hydraulic pressure in the high-pressure source passage 2 is equal to or higher than a predetermined value. Allow the hydraulic fluid to flow.

The wheel cylinder 6 is connected to the wheel cylinder passage 3 and to the reservoir passage 12b. A pressure increasing valve 16 is inserted into the wheel cylinder passage 3, and a pressure reducing valve 17 is inserted into the reservoir passage 12b. The pressure increasing valve 16 is a normally open electromagnetic valve, and the degree of opening of the wheel cylinder passage 3 is lowered as the electromagnetic force is increased and the opening degree is reduced.
The pressure reducing valve 17 is a normally closed electromagnetic valve whose opening degree is increased as the electromagnetic force increases.

A stroke simulator 18 is connected to the master cylinder passage 14 between the on-off valve 15 and the master cylinder 10. This stroke simulator applies a reaction force (stepping force) to the brake pedal 8 according to the depression amount (stroke amount) of the brake pedal 8.
FIG. 2 is a longitudinal sectional view of the stroke simulator 18. The outline of the stroke simulator 18 forms a cylinder 19, and one end of the cylinder 19 communicates with the master cylinder side. A first piston 20 is slidably provided in the cylinder 19. A first spring 21 is contracted between the first piston 20 and the other end of the cylinder 19 far from the master cylinder side. The first spring 21 biases the first piston 20 toward one end of the cylinder 19 closer to the master cylinder side, and when not braked, the initial position where the first piston 20 is one end of the cylinder 19 closer to the master cylinder side. Located in.
A liquid chamber filled with hydraulic fluid is defined between the end of the cylinder 19 on the side close to the master cylinder side and the first piston 20.

  Further, the master cylinder passage 14 between the opening / closing valve 15 and the master cylinder 10 is connected to one end of the responsiveness improving piston 22, and the other end of the responsiveness improving piston 22 is between the opening / closing valve 15 and the pressure increasing valve 16. The wheel cylinder passage 3 is connected. That is, the on-off valve 15 and the responsiveness improvement piston 22 are inserted into the master cylinder passage 14 in a parallel relationship.

FIG. 3 is a longitudinal sectional view of the responsiveness improving piston 22.
The outer shell of the responsive improvement piston 22 forms a cylinder 23, and a second piston 24 is slidably provided in the cylinder 23. One end 23a of the cylinder 23 communicates with the master cylinder side. The other end 23b of the cylinder 23 communicates with the wheel cylinder side. A space defined by the one end 23a, the inner wall of the cylinder 23, and the piston 24 forms a liquid chamber 26a filled with hydraulic fluid, and a space defined by the other end 23b, the cylinder 23, and the piston 24 is filled with hydraulic fluid. A liquid chamber 26b is formed. The gap between the outer periphery of the second piston 24 and the inner peripheral wall of the cylinder 23 is sealed by a seal ring 24s, and the working fluid in the liquid chamber 26a and the working fluid in the liquid chamber 26b are completely divided into two. A second spring 25 is contracted between the second piston 24 and the other end 23b. The second spring 25 urges the piston 24 toward the one end 23a, and when not braked, the second piston 24 is located at one end 23a, which is the initial position, as shown in FIG.

Next, the braking operation of this embodiment will be described.
In normal braking, the on-off valve 15 is in a shut-off state, and when the depression of the brake pedal 8 is detected, a motor (not shown) starts driving to generate a high hydraulic pressure in the hydraulic pump 1, and this high-pressure liquid is generated. Pressure is supplied to the wheel cylinder 6 through the high pressure source passage 2, the wheel cylinder passage 3, and the pressure increasing valve 16. On the other hand, when the hydraulic pump 1 fails, the on-off valve 15 is opened to supply the master cylinder hydraulic pressure directly to the wheel cylinder 6.

  First, in normal braking, at the initial step when the driver starts to depress the brake pedal 8, the hydraulic pressure generated by the hydraulic pump 1 corresponding to another pressure source of the present invention is still low, and the master cylinder Since the hydraulic pressure is higher than the pump hydraulic pressure, the master cylinder hydraulic pressure from the master cylinder 10 is changed to the master cylinder passage 14, the response improving piston 22, the wheel cylinder as shown by the solid line arrow in FIG. It is supplied to the wheel cylinder 6 through the passage 3 and the pressure increasing valve 16 to generate a braking force corresponding to the master cylinder hydraulic pressure.

At this time, the responsiveness-improving piston 22 is such that the pressing force to the other end 23b given by the master cylinder hydraulic pressure to the second piston 24 is larger than the biasing force at the initial position, so that the hydraulic fluid flows into the liquid chamber 26a. Then, the liquid chamber 26a is enlarged. Accordingly, the second piston 24 slides from the initial position on the one end 23a side of the cylinder 23 to the other end 23b side (wheel cylinder side).
On the other hand, the hydraulic fluid in the liquid chamber 26b to be reduced is given a pressing force from the second piston 24, and hydraulic fluid having a hydraulic pressure equivalent to the master cylinder hydraulic pressure flows out from the other end 23b to the wheel cylinder side.

  Thereafter, the hydraulic fluid generated by the hydraulic pump 1 becomes higher, and the hydraulic fluid is stored in the reservoir tank as shown by the solid line arrow in FIG. 5 after the middle step of the step where the pump hydraulic pressure becomes higher than the master cylinder hydraulic pressure. 11 is supplied to the hydraulic pump 1 through the reservoir passage 12, and the pump hydraulic pressure of the hydraulic pump 1 is supplied to the wheel cylinder 6 through the high pressure source passage 2, the wheel cylinder passage 3, and the pressure increasing valve 16. A braking force corresponding to the pump pressure is generated.

  At this time, the master cylinder hydraulic pressure that is slid in the direction of the other end 23b and the pump hydraulic pressure that is slid in the direction of the one end 23a act on the second piston 24 in the responsiveness improvement piston 22. After the intermediate step, the pump hydraulic pressure is higher than the master cylinder hydraulic pressure, so that the second piston 24 starts to slide toward the master cylinder toward the one end 23a which is the initial position.

When the second piston 24 returns to the one end 23a, which is the initial position, the second piston 24 cannot slide to the master cylinder side any more, and therefore does not slide to the master cylinder side due to the pump hydraulic pressure.
Even if the driver depresses the brake pedal 8 and the master cylinder hydraulic pressure is generated, if the master cylinder hydraulic pressure is lower than the pump hydraulic pressure, the master piston hydraulic pressure causes the second piston 24 to slide toward the wheel cylinder. It doesn't move.
If the driver returns the brake pedal 8 before the hydraulic pressure generated by the hydraulic pump 1 becomes higher than the master cylinder hydraulic pressure, the second piston 24 returns to the initial position by the action of the second spring 25, and The hydraulic fluid in the liquid chamber 26a is returned to the master cylinder side.

  Furthermore, since the on-off valve 15 is in a shut-off state, the hydraulic fluid in the master cylinder 10 flows into the stroke simulator 18 instead. For this reason, the first piston 20 in the stroke simulator 18 slides away from the initial position at one end of the cylinder 19 closer to the master cylinder, and the first spring 21 is contracted. As a result, the first spring 21 applies a reaction force to the hydraulic fluid via the first piston 20. This reaction force becomes the master cylinder hydraulic pressure, and applies a pedaling force corresponding to the pedal stroke from the master cylinder 10 through the push rod 9 and the brake pedal 8 to the driver.

  It should be noted that in the initial depression stage or after the intermediate depression stage, the pressure increasing valve 16 is normally open and the pressure reducing valve 17 is shut off, but the pressure increasing valve 16 and the pressure reducing valve 17 are controlled to open and close during anti-skid control. The That is, the anti-skid control repeatedly executes a pressure increasing mode for increasing the hydraulic pressure of the wheel cylinder 6, a holding mode for holding the hydraulic pressure of the wheel cylinder 6, and a pressure reducing mode for reducing the hydraulic pressure of the wheel cylinder 6. For this reason, in the pressure increasing mode, the pressure increasing valve 16 is opened, the pressure reducing valve 17 is shut off, and the hydraulic pressure in the wheel cylinder 6 is increased. In the holding mode, the pressure increasing valve 16 and the pressure reducing valve 17 are shut off to hold the hydraulic pressure of the wheel cylinder 6. In the pressure reducing mode, the pressure increasing valve 16 is shut off and the pressure reducing valve 17 is opened to reduce the hydraulic pressure in the wheel cylinder 6.

By the way, according to the above-described embodiment, both ends of the responsiveness improving piston 22 are connected before and after the on-off valve 15, and therefore, the pump hydraulic pressure of the hydraulic pump 1 is lower than the master cylinder hydraulic pressure of the master cylinder 10. In this case, the hydraulic fluid flows from the master cylinder side into the responsiveness-enhancing piston 22 so that the master cylinder hydraulic pressure can be supplied to the wheel cylinder 6. The responsiveness to the driver's brake operation can be improved.
In addition, when the pump hydraulic pressure subsequently becomes higher than the master cylinder hydraulic pressure or when the braking operation is stopped, the hydraulic fluid flowing into the responsiveness improvement piston 22 is returned to the master cylinder side, so that the liquid in the master cylinder 10 The mass balance matches. Accordingly, it is possible to prevent the maximum stroke of the brake pedal 8 from being shortened after the brake operation is finished and to prevent the operability from being deteriorated. The on-off valve 15 is in a shut-off state.

  Further, in this embodiment, since the second spring 25 for returning the second piston 24 in the responsiveness improving piston 22 to the initial position is provided, no pump hydraulic pressure is generated when the hydraulic pump 1 fails. Even when the hydraulic pressure on the wheel cylinder side 23b cannot urge the second piston 24 to the initial position, or when the braking operation is stopped, the second piston 24 can be returned to the initial position. Therefore, the hydraulic fluid that has flowed into the responsiveness improvement piston 22 is surely returned to the master cylinder side to prevent the pedal stroke before and after the brake operation and the initial position of the brake pedal from fluctuating.

Further, in this embodiment, a stroke simulator 18 is provided on the master cylinder passage 14 between the on-off valve 15 and the master cylinder 10. Then, by adjusting the set load of the first spring 21 and the second spring 25, the master cylinder hydraulic pressure at which the first piston 20 in the stroke simulator 18 starts to slide is changed to the second piston in the responsiveness improving piston 22. 24 was larger than the hydraulic pressure of the master cylinder at which sliding started. For this reason, as shown in the time chart of FIG. 6, at the initial step when the driver starts stepping on the brake pedal 8, the hydraulic fluid flows from the master cylinder 10 into the responsiveness-enhancing piston 22, and the pedal stroke is quickly performed. And the rise of the vehicle deceleration can be accelerated.
In the next stage, the second piston 24 in the responsiveness-improving piston 22 is pushed back to the initial position, and the pedal stroke change amount per unit time is slightly reduced.
In the final stage, the hydraulic fluid flows from the master cylinder 10 into the stroke simulator 18 and the pedal stroke increases as the driver depresses the brake pedal 8. Therefore, the pedal stroke of the brake pedal 8 can be matched with the reaction force-stroke characteristic of the stroke simulator 18.
It should be noted that an average value of the hydraulic pressure at which the pump hydraulic pressure rises and becomes equal to the master cylinder hydraulic pressure in the initial step is obtained in advance by experiments or the like, and the first piston 20 slides at a hydraulic pressure larger than this average value. The set load of the first spring 21 and the set load of the second spring 25 are adjusted so as to start the movement.

Further, in the present embodiment, the pressure increasing valve 16 is inserted into the wheel cylinder passage 3, the pressure reducing valve 17 is inserted into the reservoir passage 12b, and the pressure increasing valve 16 and the pressure reducing valve 17 are controlled to open and close, thereby enabling anti-skid control. However, the other end 23 b of the responsiveness improving piston 22 is connected to the master cylinder side with respect to the pressure increasing valve 16.
The other end 23b of the responsiveness improving piston 22 may be connected to the wheel cylinder side from the pressure increasing valve 16, but by connecting as in the present embodiment, the brake pedal 8 can be operated in the pressure reducing mode during the anti-skid control. This is a preferable mode because it is prevented from being moved by being sucked and can be reliably held even when the master cylinder pressure is higher than the holding pressure in the holding mode.
The volume of the liquid chamber 26b corresponds to the amount of liquid that the master cylinder discharges in advance through experiments or the like until the pump hydraulic pressure increases in the initial step and becomes equal to the master cylinder hydraulic pressure. If the capacity of the liquid chamber 26b to be used is increased, unnecessary parts can be prevented from being enlarged.

It is a circuit block diagram which shows the principal part of the hydraulic circuit of the hydraulic brake apparatus by this invention. It is a longitudinal cross-sectional view of the stroke simulator of the brake device. It is a longitudinal cross-sectional view of the responsiveness improvement piston of the brake device. It is a circuit block diagram which shows the transmission path | route of the hydraulic pressure of the brake device in the stepping initial stage. It is a circuit block diagram which shows the transmission path | route of the hydraulic pressure of the brake device after the stepping middle stage. It is a time chart which shows the pedal stroke characteristic of the brake pedal of the brake device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 High pressure source passage 3 Wheel cylinder passage 6 Wheel cylinder 8 Brake pedal 10 Master cylinder 11 Reservoir tank 12, 12a, 12b Reservoir passage 14 Master cylinder passage 15 On-off valve 16 Pressure increase valve 17 Pressure reduction valve 18 Stroke simulator 21 1st Spring 22 responsive piston

Claims (4)

An on-off valve is inserted in the pipe line that directs the hydraulic pressure from the master cylinder that responds to the braking operation to the wheel cylinder, and another hydraulic pressure source is provided by connecting to the pipe line part between the on-off valve and the wheel cylinder, When the braking operation occurs, the other hydraulic pressure source is driven with the on-off valve closed, and the hydraulic pressure from the hydraulic pressure source is adjusted based on the detected value of the master cylinder hydraulic pressure, and the wheel In the hydraulic brake device that is directed to the cylinder,
A hydraulic brake device comprising: a response improving means having a piston that responds to a differential pressure between a master cylinder side hydraulic pressure and a wheel cylinder side hydraulic pressure before and after the on-off valve. In the hydraulic brake device according to claim 1,
The hydraulic brake device according to claim 1, wherein the responsiveness improving means is provided with an elastic body that urges the piston in a direction cooperating with the hydraulic pressure on the wheel cylinder side of the on-off valve. In the hydraulic brake device according to claim 2,
A stroke simulator for providing a predetermined stroke / braking operation force characteristic by giving a stroke to the braking operation even when the on-off valve is closed is provided in a pipeline portion between the master cylinder and the on-off valve,
A hydraulic brake device characterized in that a stroke generation start load of the stroke simulator is made larger than a set load of an elastic body in the response improving means. In the hydraulic brake device according to claims 1 to 3,
Fluid pressure to the wheel cylinder can be supplied to and cut off from a pipe line portion between the another pressure source and the wheel cylinder, which is closer to the wheel cylinder than a connection point with the response improving means. A hydraulic brake device in which a pressure increasing valve is inserted.

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